U.S. soldiers who return from Iraq missing a leg from the thigh down are getting back on their feet a lot faster these days, thanks to the Rheo Knee. The new prosthetic joint, developed in Iceland, is designed to learn the nuances of an individual's movements and adjust itself. An innovative control module--made up of sensors, a computer chip and software--reacts instantaneously to changes in the wearer's gait, so there's less strain on the hips and back.